Touch-sensing capacity has become necessary requirement for electronic products in the up-to-date consuming market. Integrating the touch-sensing capacity with the displaying function allows these electronic products to perform desired functions when the users directly touch the display screen. Such touch display devices therefore provide the users with more visual and convenient way in manipulation. However, the rapid development of application programs and rise of the wearable touch display devices push the demand of the market to go beyond the need for the electronic devices having only the display and touch position-sensing functions. The touch-sensing capacity can be multiplex by having an extra function of sensing force-touch at the touch position to accomplish more models of manipulation.
Nowadays, most of the touch display devices have force sensors attached under the display panel to perform the force sensing function. However, this technic easily increases the thickness of the whole touch display device and the manufacturing cost, and incurs reliability issues.